An ultrasonic receiver can be used to determine its location with reference to one or more ultrasonic emitters, such as locating a mobile device having an ultrasonic receiver and being present within a retail, factory, warehouse, or other indoor environment, for example. The ultrasonic emitter(s) can transmit ultrasonic energy in a short pulse which can be received by an ultrasonic transducer (audio microphone) in the ultrasonic receiver. The use of several ultrasonic emitters distributed within the environment can be used to determine a specific location of a particular device using techniques known in the art such as measuring time-of-flight or signal strength of the emitter signals and using triangulation, trilateration, and the like, as have been used in radio frequency locationing systems.
However, having many mobile devices trying to establish their position within the environment, and interacting with all the emitters in the environment cannot be done simultaneously due to signal interference. One of the most valuable resources for a pulse-based time of flight (TOF) ultrasonic locationing system is time. Therefore, an advanced scheduler algorithm can be used for time-slicing, where each emitter can send its ultrasonic pulse, and there is a wait time for any echoes to settle before subsequent ultrasonic pulses are sent. The scheduler needs to coordinate which emitters are active at particular times so as to not interfere with nearby emitters. As a result, mobile devices are limited in how often they can update their location, i.e. location update rate. The location update rate of the system is directly tied to how efficient the scheduler algorithm is in servicing the available mobile devices that need to be located. Therefore, this solution solves the interference problem, but results in a poor location update rate.
Another problem occurs when enrolling new mobile devices into the locationing system, which requires that the scheduler be interrupted periodically to run an enrollment mode which identifies where any new devices are so that they can be incorporated into the scheduler algorithm. This will periodically interrupt the locationing system for multiple seconds, negatively impacting the system performance and update rate.
Accordingly, there is a need for a technique to locate a mobile device in an indoor environment without modifying the mobile device hardware and while eliminating the aforementioned issues. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing background.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.